262 On the Purification of Coal Gas. 
the cold body placed at the wide end, will be six times as great 
as in the reverse position.’ This, it is true, much exceeds what 
is wanted for our purpose ; but we must make some allowance for 
rays which are lost by reflection, or which do not emanate perpen- 
dicularly from the surface of the ball; and besides, it isa current 
though doubtful notion, that in the reflection of heat, the angle of 
incidence is less than that of reflection. At all events, it is hoped 
that by means of the foregoing explanation the paradox may be 
solved without the sorry aid of frigorific rays, which certainly 
deserve no encouragement in our northern climate. How soon 
they might be followed by a kindred system of /enebrific rays, it 
is not easy to say. Iam, &c. Henry MEIKLE. 
[For a P.S. sent hy the author, but which came to hand too late for in- 
sertion in this place, see Miscellaneous Intelligence at the end of the pre- 
sent Number. | 
XLII. On the Purification of Coal Gas ; on the ammoniacal 
Liquor of Coal Gas; and on some singular Products obtained 
from ihe ammoniacal Liquor. By Mr. Grores Lows, of 
Derby. 
To Mr. Tilloch. 
Sir, — Havine just read in your truly scientific and interesting 
Magazine for last month, Mr. Bolton’s communication on the 
popular subject of coal-gas, in which he honours me with the 
meed of praise in connexion with Mr. Parker for our humble en- 
deavours at perfecting this national source of light—thus far I 
can have no objection that Mr. Bolton should unite us ; and for 
myself, I beg to return him many thanks for a communication 
which evinces laborious research, judgement, and liberality. 
But when at one feli swoop he condemns the practice of passing 
gas through heated surfaces as “ faulty and injurious,”’ the credit 
due to my former communication, and to your pages of last De- 
cember which record it, demands that I should set Mr. B. right 
respecting the strange error he has fallen into, when he thus 
identifies my plan with Mr. Parker’s. If he will have the good- 
ness to refer to it, he will find that the chief view with which it 
was written, was to show in what we agreed and in what we dif- 
fered; and that the modus operandi of mine was the very re- 
verse of his! inasmuch as Mr. Parker applies the mediam of heat 
to his gas after it has passed the condenser; but in mine Le- 
fore! 
This difference, which Mr. B. has unfortunately overlooked, he 
will find, constitutes the sole cause why the former method de- 
teriorates the illuminating power of the gas, whilst the latter 
materially increases it. After this process of hyper-carbonizing 
the 
